U.S. patent number 9,561,738 [Application Number 14/131,307] was granted by the patent office on 2017-02-07 for control apparatus of electrically-driven vehicle.
This patent grant is currently assigned to Mitsubishi Electric Corporation. The grantee listed for this patent is Keiichi Enoki, Yasufumi Ogawa, Takuya Tamura. Invention is credited to Keiichi Enoki, Yasufumi Ogawa, Takuya Tamura.
United States Patent |
9,561,738 |
Ogawa , et al. |
February 7, 2017 |
Control apparatus of electrically-driven vehicle
Abstract
A control apparatus of an electrically-driven vehicle controls
an electrically-driven vehicle including a motor transmitting a
drive force to wheels, an inverter driving the motor, and a battery
supplying power to the inverter. The control apparatus includes
battery storage amount estimation means for estimating a storage
amount of the battery and motor rotation speed detection means for
detecting a rotation speed of the motor. Output terminals of the
inverter are short-circuited when the rotation speed of the motor
reaches or exceeds a predetermined rotation speed while the storage
amount estimated by the battery storage amount estimation means is
equal to or greater than a predetermined amount.
Inventors: |
Ogawa; Yasufumi (Tokyo,
JP), Enoki; Keiichi (Tokyo, JP), Tamura;
Takuya (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Ogawa; Yasufumi
Enoki; Keiichi
Tamura; Takuya |
Tokyo
Tokyo
Tokyo |
N/A
N/A
N/A |
JP
JP
JP |
|
|
Assignee: |
Mitsubishi Electric Corporation
(Tokyo, JP)
|
Family
ID: |
48167279 |
Appl.
No.: |
14/131,307 |
Filed: |
October 26, 2011 |
PCT
Filed: |
October 26, 2011 |
PCT No.: |
PCT/JP2011/074609 |
371(c)(1),(2),(4) Date: |
January 07, 2014 |
PCT
Pub. No.: |
WO2013/061412 |
PCT
Pub. Date: |
May 02, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20140156130 A1 |
Jun 5, 2014 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60L
58/15 (20190201); B60L 7/003 (20130101); B60L
15/20 (20130101); H02P 3/22 (20130101); B60L
3/04 (20130101); Y02T 10/705 (20130101); Y02T
10/7044 (20130101); Y02T 10/642 (20130101); Y02T
10/7258 (20130101); Y02T 10/72 (20130101); H02H
7/122 (20130101); Y02T 10/64 (20130101); H02P
2101/45 (20150115); Y02T 10/7005 (20130101); Y02T
10/70 (20130101); Y10S 903/903 (20130101) |
Current International
Class: |
B60L
9/00 (20060101); H02P 3/22 (20060101); B60L
11/18 (20060101); B60L 7/00 (20060101); B60L
3/04 (20060101); B60L 15/20 (20060101); G05D
1/00 (20060101); B60L 11/00 (20060101); H02H
7/122 (20060101) |
Field of
Search: |
;701/22
;318/780,515 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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112006000511 |
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Jan 2008 |
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DE |
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102008048463 |
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May 2009 |
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DE |
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2934529 |
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Feb 2010 |
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FR |
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9-47055 |
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Feb 1997 |
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JP |
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2002-291104 |
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Oct 2002 |
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JP |
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2002291104 |
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Oct 2002 |
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JP |
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2003-164002 |
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Jun 2003 |
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JP |
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2003164002 |
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Jun 2003 |
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JP |
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3751736 |
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Mar 2006 |
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JP |
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2006296068 |
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Oct 2006 |
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JP |
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2007-221885 |
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Aug 2007 |
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JP |
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2009-81958 |
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Apr 2009 |
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JP |
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2010-207053 |
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Sep 2010 |
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JP |
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2010207053 |
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Sep 2010 |
|
JP |
|
2011155743 |
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Aug 2011 |
|
JP |
|
Other References
Communication dated Sep. 2, 2014, issued by the Japan Patent Office
in corresponding Japanese Application No. 2013-540537. cited by
applicant .
Japanese Office Action (Reasons), issued Jun. 3, 2014 in Patent
Application No. 2013-540537. cited by applicant .
Communication dated Jul. 3, 2015 from the State Intellectual
Property Office of People's Republic of China in counterpart
Application No. 201180073634.4. cited by applicant .
Communication dated Jul. 14, 2016 from the German Patent and
Trademark Office in counterpart application No. 112011105776.8.
cited by applicant.
|
Primary Examiner: Smith; Isaac
Attorney, Agent or Firm: Sughrue Mion, PLLC Turner; Richard
C
Claims
The invention claimed is:
1. A control apparatus of an electrically-driven vehicle
controlling an electrically-driven vehicle that includes a motor
transmitting a drive force to wheels, an inverter driving the
motor, and a battery supplying power to the inverter, the control
apparatus comprising: a battery storage amount estimator to
estimate a storage amount of the battery; a motor rotation speed
detector to detect a rotation speed of the motor; a micro-computer
to compare the detected rotation speed with a first predetermined
rotation speed in response to the micro-computer determining that
the inverter is under a normal operation without being
short-circuited, and compare the detected rotation speed with a
second predetermined rotation speed, which is lower than the first
predetermined rotation speed, in response to the micro-computer
determining that the output terminals of the inverter are
short-circuited; and an inverter controller to short-circuit output
terminals of the inverter in response to the rotation speed of the
motor reaching or exceeding the first predetermined rotation speed
while the estimated storage amount of the battery is equal to or
greater than a predetermined amount, and wherein the micro-computer
stops applying a short-circuit to the output terminals of the
inverter in response to the rotation speed of the motor being lower
than the second predetermined rotation speed.
2. The control apparatus of an electrically-driven vehicle
according to claim 1, comprising: a battery temperature measurer to
measure a temperature of the battery, wherein the first
predetermined rotation speed is changed in response to the
temperature of the battery.
3. The control apparatus of an electrically-driven vehicle
according to claim 1, further comprising: a charging current
estimator to estimate a current value to be charged to the battery
on the basis of the rotation speed of the motor and the storage
amount of the battery; a battery temperature measurer to measure a
temperature of the battery; and a charging current upper limit
setter to set an upper limit value of the current to be charged to
the battery on the basis of the storage amount of the battery and
the temperature of the battery, wherein the output terminals of the
inverter are short-circuited when a value of the charging current
estimated by the charging current estimator is greater than the
upper limit value set by the charging current upper limit setter,
wherein the charging current estimator, the batter temperature
measurer, the charging current upper limit setter are implemented
by one or more micro-computers.
4. The control apparatus of an electrically-driven vehicle
according to claim 1, comprising: a charging current estimator to
estimate a current value to be charged to the battery on the basis
of the rotation speed of the motor and the storage amount of the
battery; a battery temperature measurer to measure a temperature of
the battery; and a charging current upper limit setter to set an
upper limit value of the current to be charged to the battery on
the basis of the storage amount of the battery and the temperature
of the battery, wherein the output terminals of the inverter are
short-circuited when a value of the charging current estimated by
the charging current estimator is greater than the upper limit
value set by the charging current upper limit setter, wherein the
first predetermined rotation speed is changed in response to the
temperature of the battery, and wherein the charging current
estimator, the battery temperature measurer, the charging current
upper limit setter are implemented by one or more
micro-computers.
5. A control apparatus of an electrically-driven vehicle
controlling an electrically-driven vehicle that includes a motor
transmitting a drive force to wheels, an inverter driving the
motor, and a battery supplying power to the inverter, the control
apparatus comprising: battery storage amount estimator to estimate
a storage amount of the battery; a motor rotation speed detector to
detect a rotation speed of the motor; a micro-computer to compare
the detected rotation speed with a first predetermined rotation
speed in response to the micro-computer determining that the
inverter is under a normal operation without being short-circuited,
and compare the detected rotation speed with a second predetermined
rotation speed, which is lower than the first predetermined
rotation speed, in response to the micro-computer determining that
the output terminals of the inverter are short-circuited; a
connection device to turn ON and OFF a connection of the battery
and the inverter; and an inverter controller to short-circuit
output terminals of the inverter in response to the rotation speed
of the motor reaching or exceeding the first predetermined rotation
speed while the estimated storage amount of the battery is equal to
or greater than a predetermined amount, and wherein the connection
device is switched OFF after an elapse of a predetermined time
since the output terminals of the inverter are short-circuited in
response to the detected rotation speed reaching or exceeding the
second predetermined rotation speed and a rotor temperature of the
motor being equal to or higher than a predetermined
temperature.
6. A control apparatus of an electrically-driven vehicle
controlling an electrically-driven vehicle that includes a motor
transmitting a drive force to wheels, an inverter driving the
motor, and a battery supplying power to the inverter, the control
apparatus comprising: a battery storage amount estimator to
estimate a storage amount of the battery; a motor rotation speed
detector to detect a rotation speed of the motor; a micro-computer
to compare the detected rotation speed with a first predetermined
rotation speed in response to the micro-computer determining that
the inverter is under a normal operation without being
short-circuited, and compare the detected rotation speed with a
second predetermined rotation speed, which is lower than the first
predetermined rotation speed, in response to the micro-computer
determining that the output terminals of the inverter are
short-circuited; a connection device to turn ON and OFF a
connection of the battery and the inverter; a rotor temperature
estimator to estimate a rotor temperature of the motor; and an
inverter controller to short-circuit output terminals of the
inverter in response to the rotation speed of the motor reaching or
exceeding the first predetermined rotation speed while the
estimated storage amount of the battery is equal to or greater than
a predetermined amount, wherein the connection device is switched
OFF after an elapse of a predetermined time since the output
terminals of the inverter are short-circuited in response to the
detected rotation speed reaching or exceeding the second
predetermined rotation speed and the rotor temperature being equal
to or higher than a predetermined temperature.
7. The control apparatus of an electrically-driven vehicle
according to claim 1, wherein the output terminals of the inverter
stop being short-circuited in response to the detected rotation
speed reaching or exceeding the second predetermined rotation speed
and a rotor temperature of the motor being equal to or higher than
a predetermined temperature while the estimated storage amount is
equal to or greater than a predetermined amount.
8. The control apparatus of an electrically-driven vehicle
according to claim 7, wherein the output terminals of the inverter
stop being short-circuited only after a predetermined time period
elapses since the output terminals of the inverter are
short-circuited.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National Stage of International Application
No. PCT/JP2011/074609, filed on Oct. 26, 2011, the contents of all
of which are incorporated herein by reference in their
entirety.
TECHNICAL FIELD
The present invention relates to a control apparatus of an
electrically-driven vehicle controlling an electrically-driven
vehicle that includes a motor driven via an inverter by using a
batter as a power supply, and more particularly, to a control
apparatus of an electrically-driven vehicle that prevents
overcharging of a battery.
BACKGROUND ART
Recently, hybrid electrically-driven vehicles using a motor and an
engine mounted thereon or electric cars driven by a motor alone are
increasing in the effort of reducing CO.sub.2 emission. These
electrically-driven vehicles using a motor mounted thereon include
an inverter to drive the motor and a battery serving as a power
supply in addition to the motor.
In these electrically-driven vehicles, the battery is charged by
regenerative power generation with the aim of extending a cruising
distance or with the aim of suppressing an increase of fuel
consumption by the engine for power generation. In regenerative
power generation, energy that is otherwise consumed as heat
generated at a brake is extracted as electric energy. Hence, the
cost incurred or fuel consumed by this power generation is zero. It
is therefore desirable to store the power generated by regenerative
power generation in the battery as much as possible.
On the other hand, many of the batteries mounted on the
electrically-driven vehicle have a property that the life becomes
shorter when charged with an overcurrent or overcharged. Hence,
when the batteries are charged, the processing to protect the
batteries from overcharging or the like is necessary.
In order to overcome this problem, Japanese Patent No. 3751736 (PTL
1) discloses a technique, according to which SOC (State of Charge)
detection means for detecting an SOC (hereinafter, referred to also
as a storage amount) of the battery is provided. In a braking mode
in which regenerative power generation is performed, regenerative
power generation is stopped when the SOC of the battery is close to
a full charge and the mode is switched to countercurrent braking.
In contrast to the regenerative power generation by which the
battery is charged with power generated by the motor, battery power
is consumed by the countercurrent braking because the motor is
driven by power running. Hence, there is no risk of overcharging
the battery. In this manner, the technique disclosed in PTL 1
prevents overcharging of the battery by regenerative power
generation.
Also, JP-A-2003-164002 (PTL 2) discloses a technique, according to
which SOC detection means for detecting an SOC of the battery is
provided. In a case where it is determined that the battery cannot
be charged (for example, when an SOC of the battery is close to a
full charge), a three-phase short circuit is applied by
short-circuiting input terminals of the motor. By applying the
three-phase short circuit, power generated by the motor is consumed
within the motor and is not charged to the battery. Hence, there is
no risk of overcharging the battery. By configuring in this manner,
overcharging of the battery by regenerative power generation is
prevented.
Further, JP-A-9-47055 (PTL 3) discloses a technique, according to
which overcharging is prevented by applying a three-phase short
circuit when a synchronous generator is under weak field control,
that is, when an inductive voltage generated by the motor is large
in comparison with a voltage across the battery. In a case where an
inductive voltage generated by the motor is large in comparison
with a voltage across the battery as above, an amount of current to
be generated cannot be controlled by the inverter. Hence,
overcharging is prevented by applying a three-phase short
circuit.
CITATION LIST
Patent Literature
PTL 1: Japanese Patent No. 3751736 PTL 2: JP-A-2003-164002 PTL 3:
JP-A-9-47055
SUMMARY OF INVENTION
Technical Problem
Incidentally, when a rotation speed of the motor is increased, a
power generation voltage (inductive voltage) of the motor is also
increased proportionately. In a case where the motor is driven by
power running, it is necessary to apply a voltage larger than the
inductive voltage by the inverter. However, because a voltage
applicable by the inverter is limited by a voltage across the
battery, a rotation speed of the motor allowed by power running
drive is limited.
On the other hand, there is a need for an electrically-driven
vehicle driven by the motor to drive the motor by power running
until the motor rotates at a high speed and this need is satisfied
by weak flux control or a step-up DC-to-DC converter. The weak flux
control is to control the motor to be driven by power running until
it rotates at a high speed by making an inductive voltage of the
motor small by changing current-passing phases and the step-up
DC-to-DC converter drives the motor by power running until it
rotates at a high speed by boosting a voltage across the battery.
When configured in this manner, in a case where the weak flux
control or boosting of the battery voltage is stopped while the
motor is driven at a high speed, an inductive voltage of the motor
becomes high with respect to an electromotive voltage of the
battery (equivalent to an open circuit voltage of the battery).
As has been described above, when a rotation speed of the motor
increases and a power generation voltage becomes larger than an
electromotive voltage of the battery, power generated by the motor
is charged to the battery by passing a commutation diode of the
inverter. In a region where a power generation voltage of the motor
becomes larger than an electromotive voltage of the battery as
above, the inverter operates equivalently to a full-wave rectifier
circuit and the motor cannot be driven by power running or
regeneration by switching the inverter (charging to the battery is
performed even when an attempt of driving by power running or
regeneration is made). In a state in which the inverter operates as
a full-wave rectifier circuit and driving is performed neither by
power running nor by regeneration as described above, there is a
problem that charging to the battery from the motor cannot be
stopped by applying countercurrent braking as by the technique
disclosed in PTL 1 and the battery is overcharged.
FIG. 12 is a view showing a relation between a motor rotation speed
and a braking torque when a three-phase short circuit is applied by
short-circuiting input terminals of the motor (in the case of a
three-phase motor, three input terminals are short-circuited). As
is shown in FIG. 12, the braking torque is known that the braking
torque during a three-phase short circuit becomes smaller in
reverse proportion to the motor rotation speed from a certain
rotation speed or greater.
For example, given a case where the technique disclosed in PTL 2 is
applied to an electrically-driven vehicle in which the motor and
the drive wheels are connected by a single speed reducer, according
to the technique disclosed in PTL 2, a three-phase short circuit is
applied independently of a rotation speed of the motor when the
battery cannot be charged. Hence, the motor rotation speed
decreases due to the three-phase short circuit and the braking
torque of the motor increases abruptly in response to a decrease of
the motor rotation speed. Accordingly, the driver needs to reduce
an amount of depression on the brake pedal in response to a
decrease of the motor rotation speed. This results in a problem
that the driver feels uncomfortable.
Further, given a case where the technique disclosed in PTL 3 is
applied to a control apparatus in the electrically-driven vehicle,
a three-phase short circuit is applied while an inductive voltage
of the motor is large in comparison with a voltage across the
battery. Hence, even when the SOC of the battery is low and there
is a good capacity for overcharging, the charging to the battery is
stopped. This results in a problem that regenerative power cannot
be used.
The invention was devised in view of the foregoing circumstances
and has an object to provide a control apparatus of an
electrically-driven vehicle, which is capable of preventing
overcharging of the battery even when a motor rotation speed is
high and an inductive voltage of the motor is larger than a voltage
across the battery without making the driver feel
uncomfortable.
Solution to Problem
In order to solve the problems above, a control apparatus of an
electrically-driven vehicle of the invention is a control apparatus
of an electrically-driven vehicle controlling an
electrically-driven vehicle that includes a motor transmitting a
drive force to wheels, an inverter driving the motor, and a battery
supplying power to the inverter. The control apparatus includes
battery storage amount estimation means for estimating a storage
amount of the battery and motor rotation speed detection means for
detecting a rotation speed of the motor. Output terminals of the
inverter are short-circuited when the rotation speed of the motor
reaches or exceeds a predetermined rotation speed while the storage
amount estimated by the battery storage amount estimation means is
equal to or greater than a predetermined amount.
Advantageous Effects of Invention
According to the control apparatus of an electrically-driven
vehicle of the invention, it becomes possible to provide a control
apparatus of an electrically-driven vehicle, which is capable of
preventing overcharging of the battery even when the motor rotates
at a high speed and a voltage generated by the motor becomes equal
to or higher than a voltage across the battery, so that the life of
the battery is not shortened.
The foregoing and other objects features, aspects, and advantages
of the present invention will become more apparent from the
following detailed description of the present invention when taken
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a view showing a configuration of a control apparatus of
an electrically-driven vehicle according to a first embodiment of
the invention.
FIG. 2 is a flowchart depicting an operation of the control
apparatus of an electrically-driven vehicle according to the first
embodiment of the invention.
FIG. 3 is a map indicating a relation between a battery temperature
and a first predetermined rotation speed of a motor.
FIG. 4 is a map indicating a relation between a stator temperature
and a rotor temperature of the motor.
FIG. 5 is a time chart depicting an operation of an
electrically-driven vehicle including the control apparatus when
the rotor temperature is low.
FIG. 6 is a time chart depicting an operation of the
electrically-driven vehicle including the control apparatus when
the rotor temperature is high.
FIG. 7 is a view showing a configuration of a control apparatus of
an electrically-driven vehicle according to a second embodiment of
the invention.
FIG. 8 is a block diagram of charging current estimation means used
in the control apparatus of an electrically-driven vehicle
according to the second embodiment of the invention.
FIG. 9 is a block diagram of charging current upper limit setting
means used in the control apparatus of an electrically-driven
vehicle according to the second embodiment of the invention.
FIG. 10 is a flowchart depicting an operation of the control
apparatus of an electrically-driven vehicle according to the second
embodiment of the invention.
FIG. 11 is a time chart depicting an operation of an
electrically-driven vehicle including the control apparatus.
FIG. 12 is a view showing a relation between a motor rotation speed
and a braking torque when a three-phase short circuit is
applied.
DESCRIPTION OF EMBODIMENTS
First Embodiment
FIG. 1 is a view showing a configuration of a control apparatus of
an electrically-driven vehicle of a first embodiment.
Referring to FIG. 1, a control apparatus 101 calculates a drive
torque of a motor on the basis of information, for example, an
amount of depression on an unillustrated accelerator pedal and a
brake stroke, and drives an inverter 102 to drive the motor at the
calculated drive torque. A battery 103 supplies power to a step-up
DC-to-DC converter 104 and the inverter 102. The step-up DC-to-DC
converter 104 supplies power to the inverter 102 by boosting a
voltage across the battery 103. A connection device (hereinafter,
referred to as the contactor) 105 formed of a contactor or a relay
device is provided between the battery 103 and the step-up DC-to-DC
converter 104. It is configured in such a manner that the battery
103 is disconnected from the step-up DC-to-DC converter 104 and the
inverter 102 when the contactor 105 is switched OFF.
The inverter 102 is formed of six switching elements, for example,
IGBTs (Insulated Gate Bipolar Transistors) and converts DC power,
which is an output from the step-up DC-to-DC converter 104, to
three-phase AC power.
Reference numeral 106 denotes a motor. An output shaft of the motor
106 is meshed with a final gear (not shown) so that a drive force
is transmitted to the wheels.
A configuration of the control apparatus 101 will now be described.
The control apparatus 101 includes a micro-computer 107, inverter
control means 108, motor rotation speed detection means 109,
battery storage amount estimation means 110, contactor operation
means 111, battery temperature measurement means 112, and rotor
temperature estimation means 113.
The micro-computer 107 determines a torque at which the motor 106
is driven on the basis of information on the unillustrated
accelerator pedal and a brake stroke, and gives an instruction to
the inverter control means 108. The inverter control means 108
determines an operation of the switching elements of the inverter
102 so as to follow a motor torque specified by the micro-computer
107.
The motor rotation speed detection means 109 calculates a rotation
speed of the motor 106 by differentiating angular information
obtained by an angle sensor, for example, a resolver.
The battery storage amount estimation means 110 estimates a storage
amount of the battery 103. The battery storage amount estimation
means 110 sets in advance an initial value of a storage amount by
measuring an open circuit voltage (OCV) of the battery 103 while
the contactor 105 is switched OFF and then detects a storage amount
by adding up a current value inputted into and outputted from the
battery 103.
The contactor operation means 111 switches OFF the contactor 105 in
a case where there is an OFF instruction for the contactor 105 from
the micro-computer 107.
The battery temperature measurement means 112 measures a
temperature of the battery 103. For example, a temperature sensor,
such as a thermistor, is provided to each cell and a maximum value
among these temperature sensors is used as the battery
temperature.
The rotor temperature estimation means 113 estimates a rotor
temperature of the motor 106. For example, a temperature sensor,
such as a thermistor, is provided inside a stator coil of the motor
106 and the rotor temperature estimation means 113 can estimate the
rotor temperature using a value of the temperature sensor by
referring to a map or by applying filtering to a value of the
temperature sensor.
The motor rotation speed detection means 109, the inverter control
means 108, the battery storage amount estimation means 110, the
contactor operation means 111, the battery temperature measurement
means 112, and the rotor temperature estimation means 113 are shown
separately from the micro-computer 107. These means can be internal
processing of the micro-computer 107.
The control apparatus of an electrically-driven vehicle of the
first embodiment is configured as above and an operation thereof
will be described next. FIG. 2 is a flowchart depicting an
operation of the control apparatus of an electrically-driven
vehicle of the first embodiment. Processing depicted in this
flowchart is performed by the micro-computer 107 at a constant
period, for example, 10 ms.
Firstly, in Step 201, whether a storage amount of the battery 103
estimated by the battery storage amount estimation means 110 is
equal to or greater than a predetermined storage amount is
determined. When the storage amount of the battery 103 is equal to
or greater than the predetermined storage amount, advancement is
made to Step 202; otherwise, advancement is made to Step 212. The
storage amount used in this determination is a storage amount
slightly short of becoming overcharged, and set, for example, to
about 80%. It is preferable to have one second predetermined
storage amount, for example, of about 75% so that this
determination is a determination with hysteresis.
In Step 202, a first predetermined rotation speed and a second
predetermined rotation speed of the motor 106 are determined on the
basis of the battery temperature detected by the battery
temperature measurement means 112. Herein, the first predetermined
rotation speed is calculated by referring to a map shown in FIG. 3
indicating a relation between the battery temperature and the first
predetermined rotation speed of the motor 106. The second
predetermined rotation speed is a value found by subtracting a
predetermined value from the first predetermined rotation speed.
The predetermined value to be subtracted is set so that the
determination is a determination with hysteresis in order to
prevent ON and OFF determinations from being repeated for a
three-phase short circuit described below. Advancement is made to
Step 203 when the first predetermined rotation speed and the second
predetermined rotation speed of the motor 106 are determined.
In Step 203, a confirmation is made as to whether it is a state in
which the contactor 105 is ON and a three-phase short circuit is
not being applied. When a three-phase short circuit is not being
applied and the contactor is ON, advancement is made to Step 204;
otherwise, advancement is made to Step 206.
In Step 204, whether a rotation speed of the motor 106 is equal to
or higher than the first predetermined rotation speed is
determined. If this determination is true, that is, when the
rotation speed of the motor 106 is equal to or higher than the
first predetermined rotation speed, advancement is made to Step
205. If the determination is false, advancement is made to Step
213.
In Step 205, the micro-computer 107 stops a torque instruction
according to an operation condition of the driver, which is the
normal control, and instructs the inverter control means 108 to
apply a three-phase short circuit. The inverter control means 108
then switches ON or OFF the switching elements so that the three
output terminals of the inverter 102 are short-circuited. When the
processing in Step 205 ends, advancement is made to END.
By applying a three-phase short circuit only when the motor 106 is
rotating at equal to or higher than the first predetermined
rotation speed in this manner, a three-phase short circuit is not
applied while the motor 106 is rotating at a low speed during which
the braking torque becomes large. It thus becomes possible to
provide a control apparatus of an electric motor that does not make
the driver feel uncomfortable.
Subsequently in Step 213, power running drive is allowed and
regenerative power generation is inhibited. In this state, power
running drive is performed as the driver wishes while the
accelerator pedal is depressed and the vehicle is accelerating or
running steadily. While the accelerator pedal is lifted and the
vehicle is decelerating, all the switching elements of the inverter
102 are switched OFF and power is not generated by the motor 106.
When the processing in Step 213 ends, advancement is made to
END.
In Step 206, whether the rotation speed of the motor 106 is higher
than the second predetermined rotation speed is determined. If this
determination is true, that is, when it is determined that the
rotation speed of the motor 106 is higher than the second
predetermined rotation speed in a region in which the inverter 102
operates as a full-wave rectifier circuit, advancement is made to
Step 208; otherwise, advancement is made to Step 207.
In Step 207, an instruction to stop the three-phase short circuit
is provided. Further, power running drive is allowed and
regenerative power generation is inhibited as in Step 213. Also,
when the contactor 105 is OFF, the contactor 105 is switched ON.
When Step 207 ends, advancement is made to END.
In Step 208, whether the rotor temperature estimated by the rotor
temperature estimation means 113 is a predetermined temperature is
confirmed. When the rotor temperature is equal to or higher than
the predetermined temperature, advancement is made to Step 209;
otherwise, advancement is made to END. The predetermined
temperature used in this determination is set to a temperature not
to cause irreversible demagnetization in permanent magnets used in
the rotor when a three-phase short circuit is applied.
In Step 209, whether a delay time since the application of the
three-phase short circuit exceeds a predetermined time is
determined. When the delay time is equal to or longer than the
predetermined time, advancement is made to Step 210; otherwise,
advancement is made to END. The predetermined time is set to a time
taken for a flowing current to become zero when a three-phase short
circuit is applied while the current is flowing from the inverter
102 to the battery 103.
In Step 210, an OFF instruction is given to the contactor control
means 111 to switch OFF the contactor 105. Then, advancement is
made to Step 211. In Step 211, the three-phase short circuit being
applied is stopped and advancement is made to END.
In this manner, the current flowing from the inverter 102 to the
battery 103 becomes zero after the three-phase short circuit is
applied. It thus becomes possible to switch OFF the contactor 105
without giving rise to a surge that occurs otherwise when the
contactor is switched OFF.
Also, by switching OFF the contactor 105 in a state in which the
rotor temperature of the motor 106 is high and by disconnecting the
battery 103 from the inverter 102, it becomes possible to prevent
demagnetization of the motor 106 while preventing the overcharging
of the battery 103.
In Step 212, in a case where the three-phase short circuit is being
applied, the three-phase short circuit is stopped and the
micro-computer 107 instructs the inverter control means 108 so that
a motor torque corresponding to an operation of the driver can be
outputted. Also, when the contactor 105 is switched OFF, the
contactor 105 is switched ON. In a case where a three-phase short
circuit is not being applied, that is, in a case where a torque
instruction corresponding to an operation of the driver is given,
advancement is made to END.
FIG. 3 shows a map indicating a relation between the battery
temperature and the first predetermined rotation speed of the motor
106. In the drawing, the battery temperature and the first
predetermined rotation speed of the motor 106 have a relation
expressed by a linear function. However, the relation is not
necessarily expressed by a linear function. The relation is
determined on the basis of an electromotive voltage (voltage across
the terminals when the battery terminals are opened, that is, an
open circuit voltage) and an inductive voltage of the motor 106 in
a state where the battery 103 is already charged to the extent over
which the battery 103 becomes overcharged.
It is known that an electromotive voltage at which the battery 103
becomes overcharged varies with a battery temperature and there is
a characteristic that the battery 103 is deteriorated when the
battery 103 is charged at a high voltage when the battery
temperature is low. Accordingly, the map of FIG. 3 is calculated by
plotting a rotation speed of the motor 106 with which an inductive
voltage of the motor 106 becomes equal to or higher than an
electromotive voltage at which the battery 103 become overcharged
at each battery temperature. It is possible to adopt a method by
which the map is calculated in advance and the first predetermined
rotation speed is calculated on the basis of the battery
temperature in this manner. However, calculations may be made
online. As has been described, by changing the first predetermined
rotation speed in response to the battery temperature, it becomes
possible to provide a control apparatus of an electrically-driven
vehicle, which is capable of preventing the overcharging in a
reliable manner even when the battery temperature varies.
FIG. 4 shows a map indicating a relation between the stator
temperature and the rotor temperature of the motor 106. In the
drawing, the relation between the stator temperature and the rotor
temperature is a relation expressed by a linear function. However,
the relation is not necessarily the one shown in the drawing. The
map is created by driving the motor alone in advance and using a
relation between the rotor temperature and the stator temperature
at the time of this driving.
FIG. 5 is a time chart depicting an operation of an
electrically-driven vehicle including the control apparatus 101
when the rotor temperature is low.
Referring to FIG. 5, A is a chart indicating a vehicle speed of the
electrically-driven vehicle. In the electrically-driven vehicle of
this embodiment, because the motor 106 is connected to the wheels
via the final gear with a fixed transmission gear ratio, the
rotation speed of the motor 106 and the vehicle speed shape
waveforms at a ratio of 1:1.
B is a chart indicating the rotation speed of the motor 106 and C
is a chart indicating a bus voltage of the inverter 102. A bus
voltage of the inverter 102 fluctuates with an operation condition
of the step-up DC-to-DC converter 104.
D is a chart indicating a battery current. The battery current is a
current flowing between the battery 103 and the step-up DC-to-DC
converter 104, which is shown on the plus side when discharged from
the battery 103 and on the minus side when charged to the battery
103.
E is a chart indicating a motor current effective value and it
represents an effective value of a three-phase AC waveform to be
passed from the inverter 102 to the motor 106.
F is a chart indicating a storage amount of the battery 103 which
is calculated by the battery storage amount estimation means
110.
G is a chart indicating a state of the contactor 105. In this
chart, the contactor 105 is constantly switched ON and therefore
the battery 103 and the step-up DC-to-DC converter 104 are
connected.
Referring to the drawing, a period from times t0 to t1 is a section
in which the motor 106 is driven at a high speed by boosting a
voltage across the battery 103 by the step-up DC-to-DC converter
104. In this instance, power running drive is performed by
extracting power from the battery 103.
At the timing of time t1, the step-up DC-to-DC converter 104 stops
the boosting operation. At this timing, the motor 106 is driven at
a high speed and an inductive voltage of the motor 106 is larger
than an electromotive voltage of the battery 103.
A period from times t1 to t2 is a section in which an inductive
voltage of the motor 106 is larger than an electromotive voltage of
the battery 103. In this section, the inverter 102 operates as a
full-wave rectifier circuit and charges the battery 103. A storage
amount of the battery 103 increases because it is charged.
At time t2, a storage amount of the battery 103 reaches a
predetermined storage amount (for example, 80%) and a three-phase
short circuit is applied to the inverter 102. A three-phase short
circuit can be applied by switching ON the IGBTs on the low side
and switching OFF the IGBTs on the high side.
In a section from times t2 to t3, the inverter 102 is three-phase
short-circuited. While the inverter 102 is three-phase
short-circuited, the bus voltage C thereof coincides with an
electromotive voltage of the battery 103. Also, the battery current
D becomes zero and is not charged to the battery 103.
In this manner, by applying a three-phase short circuit in a region
in which the rotation speed of the motor 106 is high and an
inductive voltage thereof exceeds an electromotive voltage of the
battery 103, it becomes possible to stop the charging to the
battery 103, which can in turn prevent overcharging of the battery
103.
The three-phase short circuit is stopped at time t3 because the
motor rotation speed B becomes lower than the second predetermined
rotation speed. By setting the first predetermined rotation speed
and the second predetermined rotation speed in this manner, it
becomes possible to provide a control apparatus of an
electrically-driven vehicle in which a three-phase short circuit is
not applied and stopped frequently.
At and after time t3, the motor 106 is driven in response to an
operation of the driver on the acceleration pedal or a brake
stroke.
FIG. 6 is a time chart depicting an operation of the
electrically-driven vehicle including the control apparatus 101
when the rotor temperature is high.
Referring to FIG. 6, H through N correspond to A through G of FIG.
5, respectively. P represents the rotor temperature, which is a
value estimated by the rotor temperature estimation means 113. In
the time chart of FIG. 6, the rotor temperature P is a temperature
higher than the predetermined temperature.
Referring to the drawing, operations are the same as those in FIG.
5 up to time t2. At time t3, the contactor 105 is switched OFF by
the contactor operation means 111 because the delay time since the
application of the three-phase short circuit at time t2 exceeds the
predetermined time.
In this embodiment, the step-up DC-to-DC converter 104 and the
inverter 102 alone are connected to the battery 103. However, in a
case where power is supplied to electric components of the vehicle
from a step-down DC-to-DC converter, it is preferable that the
step-down DC-to-DC converter is also switched OFF.
The three-phase short circuit is stopped at time t4. The contactor
105 is switched OFF from times t4 to t5 and the battery 103 and the
step-up DC-to-DC converter 104 are disconnected. Hence, the
inverter bus voltage J is zero. In addition, because the
three-phase short circuit is stopped, the motor current effective
value is also zero in this section.
By switching OFF the contactor 105 after the battery current K is
set to zero by applying the three-phase short circuit in this
manner, it becomes possible to prevent deterioration of the battery
caused by a surge that otherwise occurs when the contactor 105 is
switched OFF. Also, by switching OFF the contactor 105 and stopping
the three-phase short circuit while the rotor temperature P is
high, it becomes possible to provide a control apparatus of an
electrically-driven vehicle, which is capable of preventing
overcharging of the battery 103 while preventing demagnetization of
the motor 106.
At and after time t5, the motor 106 is driven in response to an
operation of the driver as in the same manner at and after time t3
of FIG. 5.
Second Embodiment
A control apparatus of an electrically-driven vehicle according to
a second embodiment of the invention will now be described.
FIG. 7 is a view showing a configuration of the control apparatus
of an electrically-driven vehicle of the second embodiment. In the
drawing, portions same as or equivalent to those of FIG. 1 are
labeled with the same reference numerals and a description is
omitted.
Referring to FIG. 7, a control apparatus 701 is of substantially
the same configuration as that of the control apparatus 101
described in the first embodiment above, and includes a
micro-computer 702, inverter control means 108, motor rotation
speed detection means 109, battery storage amount estimation means
110, contactor operation means 111, battery temperature measurement
means 112, and rotor temperature estimation means 113. It should be
noted that the micro-computer 702 is different from the
micro-computer 107 of the first embodiment above in that it
includes charging current estimation means 703 and charging current
upper limit setting means 704.
The charging current estimation means 703 estimates a current value
to be charged to the battery 103 on the basis of a storage amount
estimated by the battery storage amount estimation means 110 and
the motor rotation speed detected by the motor rotation speed
detection means 109. Also, the charging current upper limit setting
means 704 sets an upper limit value of a charging current on the
basis of the temperature of the battery 103 measured by the battery
temperature measurement means 112 and the storage amount of the
battery 103.
FIG. 8 is a block diagram of the charging current estimation means
703. The charging current estimation means 703 includes inductive
voltage computation means 801, impedance computation means 802,
battery electromotive voltage computation means 803, and charging
current computation means 804.
The inductive voltage computation means 801 computes an inductive
voltage on the basis of the rotation speed of the motor 106.
Because an inductive voltage in a permanent magnet synchronous
motor can be calculated as: (rotation speed of the
motor).times.(permanent magnet flux), this calculation is used
herein. Also, because the permanent magnet flux changes with the
rotor temperature, a correction may be made according to a value of
the rotor temperature estimation means 113.
The impedance computation means 802 computes impedance of the
inverter 102, the motor 106, and the battery 103. Factors that
determine the impedance of the inverter 102, the motor 106, and the
battery 103 include resistance in a current-passing path for the
inverter 102 and a resistance component and an inductance component
of the coil for the motor 106. Also, the factors include internal
resistance of the battery 103 for the battery 103.
From these factors, the impedance computation means 802 calculates
impedance Rz in accordance with an equation as follows: Rz=
[(R1+R2+R3)2+(WL)]2 where R1 is the internal resistance of the
battery 103, R2 is the resistance in the current-passing path of
the inverter 102, R3 is the coil resistance of the motor 106, L is
the coil inductance of the motor 106, and W is the rotation speed
of the motor 106.
Herein, the internal resistance R1 of the battery 103 can be found,
for example, by Steps (1) through (4) as follows:
(1) an electromotive voltage of the battery 103 is calculated on
the basis of the storage amount of the battery 103;
(2) an amount of current when the current flows to the inverter 102
and a voltage across the terminals of the battery 103 are
measured;
(3) a voltage drop amount is calculated from a difference between
the electromotive voltage calculated in (1) and the voltage across
the terminals of the battery 103 obtained in (2); and
(4) the internal resistance is calculated by the Ohm's law using
the amount of current of the battery 103 obtained in (2) and the
voltage drop amount calculated in (3) as: (internal
resistance)=(voltage drop amount)/(current value).
The battery electromotive voltage computation means 803 calculates
an electromotive voltage of the battery 103 on the basis of the
storage amount of the battery 103. The electromotive voltage of the
battery 103 varies with characteristics of the battery 103. Hence,
a map is created by measuring a relation between a storage amount
and an electromotive voltage of the battery 103 in advance and an
electromotive voltage of the battery 103 is computed by referring
to the map when the control is performed.
The charging current computation means 804 calculates a charging
current in accordance with an equation below using the inductive
voltage V1 computed by the inductive voltage computation means 801,
the impedance Rz computed by the impedance computation means 802,
and the battery electromotive voltage V2 calculated by the battery
electromotive voltage computation means 803, and outputs the
calculation result as an estimate value. (charging
current)=(V1-V2)/Rz
FIG. 9 is a block diagram of the charging current upper limit
setting means 704. The charging current upper limit setting means
704 is formed of first upper limit value calculation means 901 for
calculating a charging current upper limit value determined by a
storage amount of the battery 103, second upper limit value
calculation means 902 for calculating a charging current upper
limit value determined by the battery temperature, and minimum
value computation means 903.
Both of the first upper limit value calculation means 901 and the
second upper limit value calculation means 902 calculate the
charging current upper limit value using a map created in advance
by measuring, for example, the characteristics of the battery 103.
The minimum value computation means 903 outputs one of the charging
current upper limit value calculated by the first upper limit value
calculation means 901 and the charging current upper limit value
calculated by the second upper limit value calculation means 902
whichever is the smaller, that is, whichever is the stricter
limitation.
This embodiment adopts, as the charging current upper limit setting
means 704, a method by which the limit values are calculated on the
basis of the storage amount and the battery temperature of the
battery 103, respectively, and whichever the stricter limitation is
outputted. Alternatively, the upper limit value may be calculated
using, for example, a two-input map of a storage amount and a
battery temperature of the battery 103.
The control apparatus of an electrically-driven vehicle of the
second embodiment is configured as above and an operation thereof
will be described next. FIG. 10 is a flowchart depicting an
operation of the control apparatus of an electrically-driven
vehicle of the second embodiment.
Firstly, in Step 1001, the charging current upper limit setting
means 704 computes an upper limit value of the charging current. In
Step 1002, the charging current estimation means 703 estimates a
charging current.
In Step 1003, whether the estimated charging current has a value
equal to or greater than the upper limit value is determined. If
this determination is true, that is, when the charging current has
a value equal to or greater than the upper limit value, advancement
is made to Step 1004. If the determination is false, advancement is
made to Step 1005.
In Step 1004, a three-phase short circuit is applied because there
is a possibility that the charging current to the battery 103
becomes an overcurrent. In Step 1005, regenerative power generation
is allowed without applying a three-phase short circuit because the
charging current to the battery 103 does not become an
overcurrent.
FIG. 11 is a time chart depicting an operation of an
electrically-driven vehicle including the control apparatus
701.
In FIG. 11, Q is a chart indicating a vehicle speed and R is a
chart indicating a rotation speed of the motor 106. Also, S is a
chart indicating a bus voltage of the inverter 102. The bus voltage
of the inverter 102 becomes large with respect to a voltage across
the battery 103 by boosting the voltage across the battery 103
using the step-up DC-to-DC converter 104. In the drawing, an
alternate long and short dash line represents an inductive voltage
of the motor 106 and a broken line represents an electromotive
voltage of the battery 103.
T is a chart indicating a current of the battery 103. The current
of the battery 103 is a current flowing between the battery 103 and
the step-up DC-to-DC converter 104, which is shown on the plus side
when discharged from the battery 103 and on the minus side when
charged to the battery 103.
U is a chart indicating the charging current value estimated by the
charging current estimation means 703 and the charging current
upper limit value computed by the charging current upper limit
setting means 704. V is a chart indicating a state as to whether a
three-phase short circuit is being applied or not.
Referring to the drawing, in a period from times t0 to t1, the
motor 106 is accelerating and the bus voltage of the inverter 102
is increased with respect to the electromotive voltage of the
battery 103 by boosting a voltage across the battery 103 using the
step-up DC-to-DC converter 104. Also, in this instance, a current T
of the battery 103 is discharged from the battery 103 and a
three-phase short circuit is not applied.
At time t1, the step-up DC-to-DC converter 104 stops the operation
and the bus voltage S of the inverter 102 takes a value
substantially equal to the value of the electromotive voltage of
the battery 103. By stopping the step-up DC-to-DC converter 104 in
this manner, the bus voltage of the inverter 102 becomes small in
comparison with an inductive voltage of the motor 106. Also, the
charging current estimate value increases at this timing in a
charging direction and takes a value greater than the charging
current upper limit value set according to a state of the battery
103. More specifically, a three-phase short circuit is applied at
time t1 because it is determined that the battery 103 is charged
with an excessively large current.
The three-phase short circuit is applied to the inverter 102 from
times t1 to t2. Hence, the current T of the battery 103 becomes
zero. Also, in this section, a braking force is generated due to
the three-phase short circuit and the vehicle speed Q, the motor
rotation speed R, and the motor inductive voltage are
decreased.
Time t2 is a point at which the charging current estimate value
drops below the charging current upper limit value and the
three-phase short circuit is stopped at time t2. The battery 103 is
charged at and after time t2 because the three-phase short circuit
is stopped.
As has been described, by computing the charging current upper
limit value and the charging current estimate value and applying a
three-phase short circuit only in a limited case where the charging
current estimate value becomes greater than the charging current
upper limit value, it becomes possible to stop the charging only
when the battery 103 is charged with an excessively large current.
It thus becomes possible to charge the battery 103 with
regenerative power while preventing deterioration of the battery
103 by the charging with an over current.
The embodiments above described a case where the
electrically-driven vehicle is an electric car driven by the motor
alone by way of example. However, the same advantages can be
obtained when the electrically-driven vehicle is a hybrid car
driven by the engine and the motor.
It should be understood that the respective embodiments of the
invention described above can be combined without any restriction
and the respective embodiments can be modified and omitted as the
need arises within the scope of the invention.
* * * * *